1. Field of Invention
The invention relates to high power pulse transformers for microwave generators, advanced propulsion systems, electromagnetic launchers, etc., requiring energies on the order of 10 joules to be supplied within a few milliseconds.
2. Description of the Prior Act
Pulsed transformers are presently proposed as energy compression devices for the above referenced and other purposes. These transformers consist of both normal or non-superconducting primary and secondary windings and superconducting primary and normal secondary windings or portions of the primary with a pulse or discharge resistor or resistors in parallel with the primary or portions of the primary for pulsing or power transfer to the secondary winding. The pulse or discharge resistor circuit is connected across the primary for power transfer. This energy transfer between windings produces extra high voltages which severely limit the practicability of such an energy compression scheme for exceeding high power transfer due to the magnitude of the insulation required and resulting weight penalty. To compress 120 Million Joules (MJ) of energy from a normal conducting primary to a normally conductive secondary in a time span of from 2 to 5 micro seconds (MS) creates high voltage in the order of megavolts (MV) within the primary winding. Such magnitude of high voltage represents a critical design problem for an inductor transformer (I/T) system and results in an extremely heavy system because of the massive insulation needed (as aforementioned) to prevent voltage breakdown within and between windings. As a result of the insulation requirements, less than 30% of the primary winding energy is transferable to the secondary and hence to the load in state of the art transformers.
Superconductors are well known in the art since their discovery in the early twentieth century. It is known that certain materials lose all apparent electrical resistance when they are subjected to a very low temperature in the vicinity of absolute zero Kelvin. Of late, newer materials have been discovered that become superconductive at a somewhat warmer temperature (in the liquid nitrogen temperature range.) The transition from the resistive state to the superconducting state occurs abruptly at a critical temperature known as the transition temperature, the particular transition temperature differing for each material.
It is also known that a transition from a superconducting to a normal (resistive) state can be induced in a superconductor by applying a magnetic field to the superconductor; by elevating the temperature of the superconductor and by providing energy in excess of the storage capacity of the superconductor or any combination thereof.
Massive make and break electrical switches are required in the state of the art transformer schemes which work with extremely high voltage that are in the MV ranges. These switches are required to connect and insulate the energy source from the superconductor and to close the circuit to discharge the superconductor through an external resistor for energy transfer. The design of these switches for high current and high voltage have yet to reach the practical stage of development. In most cases, switches handling this level of MV and MA cannot be used respectively.
Examples of prior art device, using superconductive primary and normal secondary are taught by U.S. Pat. Nos. 3,360,692; 3,800,256 and 4,486,800.
Because of the inefficient energy transfer and the unavailability of practical MV and MA switches, the use of a superconductor as a primary of a highly efficient high power pulse transformer capable of multiple or continuous pulsing to a secondary connected load has not been available until the emergence of this instant invention.